In the manufacture of transit vehicles, such as buses and rail cars, a presently preferred practice employs side wall structures, at least the lower portions of which are covered with extruded aluminum strakes. The strakes are secured to a supporting frame, and a floor structure is provided comprising a sandwich panel slab with a structural plastic foam core and top and bottom facing sheets of suitable material, for example, aluminum or stainless steel. In my U.S. Pat. No. 3,815,306, assigned to the Assignee of the present invention, a floor slab of such general nature is disclosed, with an outwardly open channel secured between laterally outwardly extending edge portions of the upper and lower facing sheets along each side of the slab. A tapered bead is formed along the upper flange of each side channel, and is seated in a recess provided therefor along a lower, inwardly facing surface of each side wall, while the lower flange of each side channel is provided with a downwardly extending riveting flange, which seats against, and is riveted to, its respective side wall.
Such floor mounting arrangement, while providing great strength and rigidity, and being relatively simple to assemble, still requires the drilling or punching of a large number of rivet holes, and the seating of the rivets therein to complete the assembly. The present invention is a substantial improvement over such joint structure, and provides strong, rigid, interconnection between the floor and side wall structure of a transit vehicle, which interconnection is of uniform strength throughout its length, perfectly sealed, and entails substantially reduced material costs and labor input. In accomplishing this improvement the invention employs a plastic key interlock joint structure of the same general nature as that disclosed in my co-pending application, Ser. No. 594,828, filed July 10, 1975 now U.S. Pat. No. 3,992,846 , and assigned to the assignee of the present invention.